Superheater control



Aprll 22, 1952 M. FRISCH 2,593,435

SUPERHEATER CONTROL Original Filed Nov. 12, 1941 2 SHEETS-SHEET 1 7f/ 86 me INVENTOR A TTOR Y April 22,1952 M. FRISCH 2,593,435

SUPERHEATER CONTROL Original Filed Nov. 12, 1941 2 SHEETS-SHEET 2 lyz 88 93 F- 9 at //4 l I l l l l l "lll l lll l i l lfl l l l l INVENTOR Patented Apr. 22, 1952 UNITED STATES PATENT, OFFICE SUPER-HEATER CONTROL Martin Frisch, New York, N. Y., assignor to Foster Wheeler Corporation, New York, N. Y., a corporation of New York I 7 Original application November 12,1941, Serial No. 418,650. Divided and this application Au gust 2, 1946, Serial No. 688,094

culation at all times including immediate cir-' culation when the generator is started up.

, This invention also provides a forced circulation type vapor generator in which the tubes of the steam generating and the superheating sections are so arranged that there are a plurality of main paths of flow from the inlet to the outlet of each section, with the lengths of the flow paths in each section substantially equal and with the flow through each section and each path of each section generally concurrent to the flow of gases.

f The present application is a division of application Serial No. 418,650 filed November 12, 1941, now Patent No. 2,495,573 issued August 13, 1946.

The invention will be understood from the following description when considered in connection with the accompanying drawings forming a part thereof, and in which:

- Fig. 1 is a vertical sectional view, more or less diagrammatic, of a forced recirculation steam generator embodying the invention;

Fig. 2 is an enlarged vertical sectional view of the upper portion of the separating and circulating device shown in elevation in Fig. l, and Fig. 3 is a vertical sectional view of the lower portion of the separating and circulating device. Like characters of reference refer to like parts throughout the several views.

- Referring to Fig. 1, the setting of the generator shown, has opposite side walls I! and [2, a roof l3, and a gas outlet M. An economizer IS in the outlet 14 is connected to a feed water'conduit l6 leading from the discharge side ll of a feed pump is which is driven by a motor l9 connected to a source of electricity, not shown. Feed water entersthe pump l8 at the suction side thereof, and is forced through conduit [6 and through the economizer [5 in a direction of flow countercurrent-to the direction of flow of the heating gases into an'outlet conduit 2| which is connected to a separating and circulating device 22. As shown, the separating and circulating device comprises an elongated, vertically disposed, housing 23 having a fluid chamber 24 therein and a 6 Claims. (01. 122-419) circulatingpump casing 25 at the bottom of the a cap having a hollow extension 3|.

housing.

, The lower end of the chamber 24 is connected by, a passage '28 with a chamber 29 in the casing.- The lower endof the casing 25 is closed by Cap 30 has an annular flange 32 which projects into the chamber 29, and engages a partition 33 holding it tightly against an annular shoulder 34 to divide the chamber 29 into two separate chambers, a

' circulating pump chamber 35, and a water turbine chamber 36. A drive shaft 31 having a reduced lower end portion 38 rotatably mounted in a thrust bearing 39 is disposed in the closed end of the cap 3! in fluid-tight relationship thereto, and extends through the chambers 24, and 36. The shaft 31 is hollow throughout the greater part of its length with solid end portions, but it may be solid throughout the entire length thereof, if desired.

' and an outlet conduit l5 conducts water from the chamber to the suction side of the feed pump IS.

A circulating pump impeller 46 is fixed to the shaft 31 above the water turbine and in the chamber 35. The impeller 46 has a plurality of blades 48 which are curved downwardly and outwardly from the passage 28 to the periphery of the impeller. Feed water flows into the impeller from the chamber 24 and is discharged into a feed conduit 52 which conducts circulating water to the steam generating section of the generator. As shown, the tubes of the steam generating section are arranged to provide two main paths of flow in parallel, from the inlet header 53 to the outlet header 54. One main path comprises tubes 55 which are connected to a fitting 55 having communication with the inlet header 53, and which extendvertically upwardly in a single row at about the center of the setting and then extend horizontally toward the wall I I to define one side and the top of a boiler furnace 57. There after the tubes 55 extend in a plurality of superposed and horizontal rows over the boiler furnace and in a plurality of additional superposed and horizontal rows substantially entirely across the setting to the outlet fitting 58 which is connected to the outlet header 54. The other main path comprises tubes 59 which extend from the inlet fitting 55 horizontally along the bottom of the boiler furnace 51 in a single row and then vertically upwardly in a single row along the wall I l to a point above the first two horizontal rows of the tubes 55, after which they extend in a plurality of superposed and horizontal rows above the boiler furnace and thereafter in like manner substantially entirely across the setting to the outlet fitting 58. The tubes in the hor-v izontal rows above the boiler furnace are stag gered, that is, with the tubes in alternate rows at a different elevation as compared with the elevation of the tubes in the other rows.

The tubes of the superheating section are arranged similarly to those of the steam generating section excepting that they do not extend entirely across the setting. The superheater inlet header 60 adjacent the inlet header 53 is connected to an inlet fitting 6| to which the superheater tubes 01 both main paths are connected. Tubes 82 extend vertically upward in a single row adjacent the tubes 55 to the elevation of the lowermost horizontal row of tubes 55, and then turn and extend horizontally to the wall [2 of the setting to define one side and the top of a superheater furnace 56. Thereafter, the tubes 62 extend in a plurality of superposed and horizontal rows to anoutlet fitting 65 which is connected to a superheater outlet header 66 from which the superheated steam flows to the point of use through a conduit 61. Tubes 63 extend along the bottom and a side of the superheater furnace and in a plurality of superposed and horizontal rows to the outlet fitting 65. The horizontal rows of the superheater tubes are staggered in the same manner the tubes of the horizontal rows of the steam generating section are staggered.

The rear wall of both furnaces 51 and 64 are lined with water tubes, not shown, which are connected in the circulatory system so as to be supplied with water from header 53 and to deliver fiuid to the outlet header 54.

With this arrangement of the tubes of the steam generating and superheating sections, the paths of flow through the tubes 55 and 59 are substantially equal and the paths of flow through the tubes 62 and 63 are also substantially equal, with the flow through each of these groups of tubes generally in the direction of flow of the gases of combustion.

The boiler and superheater furnaces are separately fired, the gases produced in the boiler I furnace 57 flowing through the furnace and over the horizontal rows of tubes 55 and 59 to the outlet 14 and over the economizer l therein. The gases produced in the superheater furnace 64 flow through the furnace and over the horizontal rows of the tubes 62 and 63 and then over the horizontal rows of tubes 55 and 59 of the steam generating section and to the outlet [4. The tubes 55 and G2 are arranged, with or without other wall or baffle means, to prevent the flow of gases from one furnace to the other.

The mixture of steam and water discharged from the steam generating section is conducted by a conduit 68 to the upper part 69 ofv the separating and circulating device 22, and is delivered tangentially into a separating chamber therein which communicates at its lower end with the upper part of chamber 24 in the housing 23. A tubular member ll of lesser diameter than the chamber IE1 and having a passage 12 therein is disposed in the chamber 10, and as shown, is provided with a peripheral flange 14 which is received in a recess in part 69 to support the tubular member in position. A mechanical steam and water separator 91, Fig. 2, is provided as shown by a plurality of radial blades 98, fixed to shaft 3? in chamber 1i closely adjacent the lower end of the tubular member H in the path of steam flowing from the separating chamber 10. Other forms of separators may be employed. The tubular member 1! projects upwardly into a hollow cap 15 which closes the upper end of part 69, to a point short of the upper end thereof, thereby forming a space It between the end of the tubular member and the cap. A cylindrical member 7! is secured at its upper end to the upper end of member H and extends downwardly in the member 'H- in spaced relationship to the inner wall thereof to provide an annular steam by-pass passage 13. The interior of member ll provides a main steam passage 78, which communicates with the space '16, for steam flowing from the passage 12. A plurality of spaced stationary turbine blades i9 disposed at the lower end ofthe member Ti, and a plurality of rotatable blades fixed to shaft 3! above the blades 79 provide a steam turbine 8| which is operated by steam flowing from passage 12 into passage I8. A steam conduit 32 which conducts steam from the separating device to the inlet header 69 of the superheater, is connected at its inlet end to the space 15 through a branch conduit 83 and to passage 12 through a by-pass conduit 84, the conduits 93 and 84 being controlled by a slide valve 85 which is actuated by a pressure responsive device 86, Fig. 1.

The upper end of drive shaft 3'! extends through the passages 72 and i8 and is rotatably.

mounted in a thrust bearing 88 in a projection 89 on cap l5. A housing 90 forms a chamber 9i around the bearing 88 and the shaft 37. Bearing 88 is cooled by feed water from a heat exchanger 92, Fig. 1, which is conducted to the bearing through a conduit 93. Bearing 39 at the lower end of the shaft 3: is cooled also by feed water from heat exchanger 92 conducted to the bearing through conduits 93 and 94. Water is withdrawn from chamber 9| through a conduit 95 controlled by a valve 95. Shaft 31 is also supported above the circulating pump 46 in a bearing 49 to which cooled feed water for lubrication is supplied by conduit 96. The feed water supplied to the bearings 39 and 40 after lubricating these bearings, mixes with the water discharged from the auxiliary turbine and the water discharged by the circulating pump, respectively. Heat exchanger 92 is connected to feed water conduit l6 through a conduit 93 and a cooling medium is supplied thereto through a conduit s2 and is withdrawn therefrom through a conduit 92".

A trap I Hi, Fig. 3, is secured in the lower portion of the chamber 24 above the point at which the economizer outlet conduit 2! is connected to the housing 23. The trap is shaped to provide a passage around the shaft 31 through which water will flow from chamber 24 into the passage 28 and the circulating pump 43. A blow-down conduit lll connects with the bottom of the trap and is controlled by a valve I 18.

The quantity of water delivered to the auxiliary water turbine and the quantity of steam floWing to the steam turbine is varied in response to variations in the quantity of water delivered to the steam generating section by the circulating pump. To this end, a flow nozzle 19!, Fig. 1, is positioned in the feed water conduit 52 and pressure conduits I02 and H13 connect opposite sides -of the-nozzle Ill'l with opposite sides of the diaphragm of a pressureresponsive device I04 which controls the flow of water in the outlet conduit 45 through apvalve I 05. Conduits I06 and 101 connect opposite sides of the diaphragm of pressure responsive device 86 with the conduits I02 and I03 respectively. The pressure responsive devices I04 and 86 are so arranged that an increase in the .fiow of circulating water through theconduit 52 will cause the device I04 to operate the valve I05 to decrease the flow of water through conduit 45 and to the auxiliary water turbine, and at the same time to cause the device 86 to operate the valve 85 to decrease the flow of vapor through the by-pass conduit 84 thereby increasing the flow through the branch Y conduitv 83 and to the steam turbine. A decrease in the flow of circulating water through the conduit, 52 will have the opposite effect.

The quantity of feed water is regulated in response to the rate of steaming. To accomplish this, a flow nozzle I08, Fig. 1, is positioned in the steam conduit 82 and opposite sides of this ori fice' vare connected by conduits I09 and H to opposite sides of the diaphragm of a pressure responsive device III which operates a valve II2 in conduit I6 to control the flow of feed water to the economizer I5. An increase in the flow of steam through the conduit 82 will cause the device III to actuate valve II2 to permit an increase in the flow of water to the economizer, and

vice versa, a decrease in the flow in the conduit 82 will cause a decrease in the flow of water to the economizer.

Valve II2 is also actuated independently of the pressure responsive device III to regulate the level of water to the chamber 24 of the separating and circulating device 22, irrespective of variations in the rate of steaming. This is accomplished by an auxiliary feed control pressure responsive device II3 which is in communication with a liquid level controller II4 through a tube II5. The level controller I I4, which is of the vapor-pressure type, has a control tube H6 therein which communicates with the chamber 24 at points above and below the normal water level therein. As the water in chamber 24 rises to a predetermined level, the device II3 actuates the valve I I2 to decrease the flow of water to the economizer I5 through conduit I6 and to the chamber 24, and when the water falls below the predetermined level, the valve is actuated to permit an increased flow of water to the economizer and the chamber 24.

The boiler furnace 51 is fired by a fuel burner I24 to which fuel is supplied through a fuel line I26, while the superheater furnace 64 is fired by a fuel burner I25 to which fuel is supplied throughfuel lines I26 and I21. Positioned in the fuel line I26 between the source of fuel supply and the burners I24 and I25, is a control valve I28 actuated by a pressure responsive device I which operates in response to the pressure in the superheater steam outlet conduit 61 and is connectedthereto through a tube I30. Valve I28 is actuated to permit an increased fiow of fuel to the burners when the vapor pressure in the conduit 61 decreases and to decrease the flow of fuel to the burners when the vapor pressure in the conduit 61 increases. A control valve I 3| similar to valve I28, controls the feed conduit I21. Valve I 3I is operated by an actuating device I32 which is responsive to the temperature in the superheater vapor outlet 61 and is connected thereto through a line I33. Upon an increase in temperature the conduit 61, the valve I3I is actuated to decrease the flow of fuel to the burner I and upon a decrease in temperature,

An orifice I34 is disposed in the fuel line I25 between the valve I28 and the source of fuel supply. Opposite sides of the orifice are connected through lines I35 and I36 to a pressure responsive actuating device I31, which operates through a rack and pinion mechanism, a damper I36 in an air conduit I40 which conducts air to the burners I24 and I25. A branch conduit I4I connects the conduit I40 with the burner I24. The arrangement is such that an increase in the fiow of fuel to the burners through line I26, will cause the pressure device I31 to actuate the damper I39 to permit an increased flow of air to the burners, while a decrease in the flow of fuel in line I26, will cause the damper I36 tobe actuated to decrease the fiow of air to the burners. An auxiliary pressure responsive device MI is connected to opposite sides of an orifice I42 in air conduit I40 by tubes I43 and I44, and operates in conjunction With the device I31 to control the damper I39.

An orifice I45 in the fuel line I21 to the superheater burner I25, has its opposite sides connected to a pressure responsive device I48 which actuates through rack and pinion mechanism, a damper I49 in the air conduit I40 to increase and decrease the quantity of air flowing to the burner I25 in response to variations in the fiow of fuel to the burner, an increase in the flow of fuel causing the damper to move to a more open position to permit a greater quantity of air to flow to the burner, While a decrease in the flow of fuel will cause the damper to move to a more closed position to decrease the quantity of air delivered to the burner. An auxiliary pressure responsive device I50 is connected across an orifice I5I in the conduit I40 and operates in conjunction with the device I48 to control the damper I40.

The means for controlling the supply of fuel and air to the burners I 24 and I25 operates automatically to supply air and fuel to each burnerin the proper amount to maintain the desired rate of steam generation. If the desired rate is exceeded, the control means will operate automati-' cally to cause a decrease in the supply of fuel and device.

manually, or by automatic means other than that disclosed, if desired.

In operation, feed Water is forced through con duit I6 by feed pump I8 into and through the economizer I5 and conduit 2| into the lower part of chamber 24 of the separating and circulating Simultaneously, feed Water is forced through conduit 44 and over the auxiliary water turbine M to rotate the shaft 31 and the circulating pump 46. Water discharged by the turbine 4I flows through conduit 45 and is returned to the pump I8 through fully open valve I05.

Heated feed water delivered into the chamber 24 through conduit 2|, fiows downwardly to the cir- In addition to this- 52 into and through the tubes 55 and 59 of the steam generating section of the generator.

The steam generated together with unvaporized water flows through conduit 68 into. the. chamber 10 of the separating and circulating device and flows in a spiral path through the chamber, causing the water and solids, entrained in the steam to be separated from the steam. The separated water and solids flow down into the chamber 24 where the separated solids are deposited in the trap H6 and are removed through. the blow-down valve I Hi. The Water flows into the water in the lower part of chamber 24. andis recirculated through. the tubes. of the steam generating. section by the pump 46 with theheated feed water from the economizer. The separated steam in chamber 10, flows over the rotating blades 9.8 which effects a further separation of Water and entrained solids from the steam, and thereafter flows upwardly through passage 12. upon the position of valve 85, the steam in passage 12 will flow through passage 13 and by-pass 84, or it will, flow to the steam turbine and through passage 18 and passage 83, or through both these paths of flow. When the generator is started up,

valve 85 is positioned to permit maximum flow of vapor through the by-pass 84 inasmuch as the circulating pump is being driven by the Water turbine. Flow of steam from passage 12 into passage I8 drives turbine 80 and the shaft 31. The steam flowing through passage 83, by-pass 84, or both, flows through conduit 82 into and through the tubes of the superheater and through c'onduit 6'! to the point of use.

Steam flowing into passage 78 will rotate the turbine 8| and the shaft 31 at a greater speed than that at which the shaft is driven by the. Water turbine 4|, so that as soon as steam is produced in sufficient quantity to drive the shaft 3'!- by the turbine 8|, the speed of shaft 31 will increase and the circulating pump 45 will be driven faster and circulating water will be forced into and through the conduit 52 and the steam generating section at a higher velocity than when the circulating pump is driven by the water turbine. This increasein the flow of water through the conduit 52 and the flow nozzle UH therein causes the device I04 to move the valve in line 65 toward; closed position, thereby reducing the quantity of water delivered to the water turbine 4i. Simultaneously, the pressure responsive device 85; actuates the valve 85 to decrease the flow of steam through the by-pass conduit 84 and to increase the flow of steam to the steam turbine 8|, thereby increasing the speed of rotation of the shaft 31 and the circulating pump 46. Consequently, as the load and the rate of evaporation increases, the quantity of steam delivered to the steam turbine progressively increases and the quantity of water delivered to the Water turbine progressively decreases, until at maximum load the quantity of water delivered to the water turbine is suflicient only to provide substantially the minimum circulation in the water turbine chamber 36 to prevent boiling due to the churning of the water therein resulting from the rotation of the water turbine.

As the angular velocity of the shaft 3'! increases because of a greater flow of steam to the steam turbine, valve H2 in feed line It to the ammomizer is operated to increase the flow of water circulated by the circulating pump and through the flow nozzle I01, pressure responsive device HM and valve I05, to decrease the flow to the water turbine, and vice versa, with the result that Depending 8 in starting the generator, the water turbine drives the circulating pump and after starting, the separated saturated steam drives the circulating pump. Specifically, when the generator is started up, the valve H2 is in a position to permit the minimum required circulation of water through the steam generating section, but as the rate of steaming increases, pressure responsive device I i I operates to move valve H2 toward open position to increase the circulation, until at the maximum rate of evaporation, valve I I2 is nearly fully open. Contraiwise, a drop in load will cause valve H2. to move toward closed position to decrease. the circulation through the steam generating sec.-'

tion. Valve H2 also functions in response. to the. device I I3 to maintain the desired water. level in.

the chamber 24 of the separating and circulating device 22. If the level drops, valve H2 will open to increase the circulation through the economizer and the quantity of water delivered to the. lower part of chamber 24, while if the level is raised, valve l l2 will move toward closed position to decrease the flow of water into the chamber 24.

Although the invention is disclosed in connection with a forced recirculation steam generator, it is applicable also to other types including once through generators.

It will be understood that the form of the invention disclosed is a preferred form and that changes may be made in the form, location andrelative arrangement of the several parts of the apparatus disclosed without departing from the principles of the invention. Accordingly, the invention is not to be limited excepting by the scope of the appended claims.

What is claimed is:

1. A separately fired vapor superheater comprising a setting, a furnace in the setting, means for firing the furnace, a superheater in the furnace, said superheater having separate sections, each section of the superheater comprising tubular members forming paths of flow separate from one another, the tubular members of one section of the superheater extending from an inlet disposed at the lower portion of the setting and at one side of the superheater furnace, upwardly along said one side of the superheated furnace thence transversely of said furnace in superposed, spaced substantially horizontally extending and connected rows above the superheater furnace to an outlet at the opposite side of the furnace, the tubular members of the other section of the superheater extending from said inlet to the side of the superheater furnace opposite said one side, upwardly along said opposite side thence transverse- 1y of said furnace and within said space between the tubular members of said one section, the tubular members of said other section being disposed in superposed, spaced substantially horizontally extending and connected rows and extending to and into communication with said outlet.

2. A separately fired vapor superheater comprising a setting, a furnace in the setting, burner means for firing the furnace, said furnace having a gas outlet in the upper part thereof, a superheater in the furnace, said superheater havin separate sections, each section of the superheater comprising tubular members forming paths of flow separate from one another, the tubular members of one section of the superheater extending from an inlet disposed at the lower portion of the setting and at one side of the superheater furnace, upwardly along said one side of the superheater furnace thence transversely of said furnace intermediate said burner means and said 9 gas outlet and in the path of gases of combustion flowing from said furnace to the outlet, said transversely extending tubular members being in superposed, spaced substantially horizontally extending and connected rows above the superheater furnace and extending to an outlet at the opposite side of the furnace, the tubular members of the other section of the superheater extending from said inlet horizontally along the floor of said furnace to the side of the super' laterally of the generator furnace, a superheater in said superheating furnace, means for firing each furnace, said superheater having separate sections, each section of the superheater com prising tubular members forming paths of flow I separate from one another, the tubular members of one section of the superheater extending from an inlet disposed at the lower portion of the setting and at one side of the superheating fur-- nace, upwardly along said one side of the super heater furnace thence transversely of said furnace in superposed, spaced substantially horizontally extending andconnected rows above the superheater furnace to an outlet at the opposite side of the furnace, the tubular members of the other section of the superheater extending from said inlet to the side of the superheater furnace opposite said one side, upwardly along said opposite side thence transversely of said furnace and within said'space between the tubular memhers of said one section, the tubular members of said other section being disposed in superposed, spaced substantially horizontally extending and connected rows extending to and into communication with said outlet, said vapor generator having separate sections, each sectionof the vapor generator "comprising .tubes forming paths of flow separate from one another, the tubes of one section of the vapor generator extending transversely of the generator furnace in superposed, spaced substantially horizontally extending and connected rows, the tubes of the other section of the vapor generator extending transversely of the generator furnace within said space between the tubes of said one section, the tubes of said other section being disposed in superposed, spaced substantially horizontally extending and connected rows, the tubes of both sections having a portion laterally adjacent the tubes of the superheating section and in heat exchange relationship with gases of combustion generated in the vapor generator furnace only, and another portion extending above both the superheater and said first-mentioned portion of the vapor generator and in. heat-exchange relationship with gases of combustion generated in both the vapor generator and superheating furnaces.

4. A vapor generator comprising a setting having a vapor generator furnace therein, a vapor generator in said generator furnace, a superheater furnace, a superheater in said superheater furnace, said vapor generator and superheater furnaces being laterally disposed in relationship to one another in the furnace, burner means associated with each of said furnaces, said setting having a gas outlet therein above the furnaces and disposed to receive gases of combustion therefrom, said superheater having separate sections, each section of the superheater comprising tubular members forming paths of flow separate from one another, the tubular members of one section of the superheater extending from an inlet disposed at the lower portion of the setting and at one side of the superheater furnace, upwardly along said one side of the superheater furnace thence transversely of said furnace intermediate said burner means and said gas outlet and in the path of gases of combustion flowing from said furnace to the outlet, said transversely extending tubular members being in superposed, spaced substantially horizontally extending and connected rows above the superheater furnace and extending to an outlet at the opposit side of the furnace, the tubular members of the other section of the superheater extending from said inlet horizontally along the floor of said furnace to the side of the superheater furnace opposite said one side, upwardly along said opposite side thence transversely of said furnace and within said space between the tubular members of said one section, the tubular members of said other section being disposed in the path of gases flowing from said furnace to the gas outlet and in superposed, spaced substantially horizontally extending and connectedv rows extending to and into communication with said outlet, said vapor generator having separate sections, each section of the vapor generator comprising tubes forming paths of flow separate from one another, the tubes of one section of the vapor generator extending from an inlet disposed at the lower portion of the setting transversely of said generator furnace along the floor thereof thence upwardly along one side of said generator furnace thence horizontally intermediate said burner means and said gas outlet to and in communication with an outlet, the tubes of the other section of the vapor generator extending from said inlet along the side of the vapor generator furnace opposite said one side, upwardly along said opposite side, thence horizontally within said space between the tubular members of said one section of the vapor generator, the tubular members of said other sec tion being disposed in superposed, spaced substantially horizontally extending and connected rows and extending to and into communication with said outlet, the tubes of both sections having a portion laterally adjacent the tubes of the superheating section and in heat exchange relationship with gases of combustion generated in the vapor generator furnace only, and another portion extending above both the superheater and said first-mentioned portion of the vapor generator and in heat exchange relationship with gases of combustion generated in both the vapor generator and superheating furnaces.

5. A vapor generator comprising aforced cir culation vapor generating section, a superheating section, a generator furnace, a vapor generator in said generator furnace, a superheating furnace disposed laterally of the generator furnace, a superheater in said superheatin-g furnace, burner means for firing each furnace, circulating means for delivering liquid to the vapor gencrating section, means for actuating the circulating means, said superheater having separate sections, each section of the superheater comprising tubular members forming paths of flow separate from one another, the tubular members of one section of the superheater extending from an inlet disposed at the lower portion of the setting and at one side of the superheater furnace, upwardly along said one side of the superheater furnace thence transversely of said furnace in superposed, spaced substantially horizontally extending and connected rows above the superheater furnace to an outlet at the opposite side of the furnace, the tubular members of the other section of the superheater extending from said inlet to the side of the superheater furnace opposite said one side, upwardly along said opposite side thence transversely of said furnace and within said space between the tubular members of said one section, the tubular members of said other section being disposed in superposed, spaced substantially horizontally extending and connected rows extending to and into communication with said outlet, said vapor generator having separate sections, each section of the vapor generator comprising tubes forming paths of flow separate from one another, the tubes of one section of the vapor generator extending transversely of the generator furnace in superposed, spaced substantially horizontally extending and connected rows, the tubes of the other section of the vapor generator extending transversely of the generator furnace within said space between the tubes of said one section, the tubes of said other section being disposed in superposed, spaced substantially horizontally extending and connected rows, the tubes of both sections having a portion laterally adjacent the tubes of the superheating section and in heat exchange relationship with gases of combustion generated in the vapor generator furnace only, and another portion extending above both the super-heater and said first-mentioned portion of the vapor generator and in heat exchange relationship with gases of combustion generated in both the vapor generator and superheating furnaces.

6. A vapor generator comprising a forced circulation vapor generating section, a superheating section, a generator furnace, a vapor generator in said generator furnace, a superheating furnace disposed laterally of the generator furnace, a superheater in said superheating furnace, burner means for firing each furnace, circulating means for delivering liquid to the vapor generating section, means for actuating the circulating means, said superheater having separate sections, each section of the superheater comprising tubular members forming paths of flow separate from one another, the tubular members of one section of the superheater extending from an inlet disposed at the lower portion of the setting and at one side of the superheater furnace, upwardly along said one side of the superheater furnace thence transversely of said furnace intermediate said burner means and said gas outlet and in the path of gases of combustion flowing from said furnace to the outlet, said transversely extending tubular members being in superposed, spaced substantially horizontally extending and connected 12 rows above the superheater furnace and extending to an outlet at the opposite side of the furnace, the tubular members of the other section of the superheater extending from said inlet horizontally along the floor of said furnace to the side of the superheater furnace opposite said one side, upwardly along said opposite side thence transversely of said furnace and within said space between the tubular members of said one section, the tubular members of said other section being disposed in the path of gases flowing from said furnace to the gas outlet and in superposec, spaced substantially horizontally extending and connected rows extending to and into communication with said outlet, said vapor generator having separate sections, each section of the vapor generator comprising tubes forming paths of flow separate from one another, the tubes of one sec tion of the vapor generator extending from an inlet disposed at the lower portion of the setting transversely of said generator furnace along the floor thereof thence upwardly along one side of said generator furnace thence horizontally intermediate said burner means and said gas outlet toand in communication with an outlet, the tubes of the other section of the vapor generator extending from said inlet along the side of the vapor generator furnace opposite said one side, upwardly along said opposite side, thence horizontally and within said space between the tubular members of said one section of the vapor generator, the tubular members of said other section being disposed'in superposed spaced substantially horizontally extending and connected rows and extending to and into communication with said outlet, the tubes of both sections having a portion laterally adjacent the tubes of the superheating section and in heat exchange relationship with gases of combustion generated in the vapor generator furnace only, and another portion extending above both the superheater and said firstmentioned portion of the vapor generator and in heat exchange relationship with gases of cornbustion generated in both the vapor generator and superheating furnaces.

MARTIN FRISCH.

REFERENCES CITED The following references are of record in the file of this patent:

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